Identification
A long white day is followed by a white day that gaps above the first day. The next two days continue in the same direction with higher consecutive closes. The final day is a long black day that closes in the gap between the first and second days.

The Psychology
In an uptrend or within a bounce of a downtrend, the stock exhausts itself with a gap up, but although the upward movement continues, it slows noticeably. The long black day suggests a possible reversal in the making to at least fill the gap. Declining volume on the three middle days with a pickup in volume on the black day serve as confirmation.